Terrain serves three roles: the theater upon which your units battle rival civilizations, the landscape across which your units travel, and the medium which your cities work to produce resources. The different types of terrain each have different strengths and drawbacks; see the sections on each terrain type for details.
Terrain affects combat very simply: when a unit is attacked, its defense strength is multiplied by the defense factor ("bonus") of the terrain beneath it. (However, some types of units do not enjoy this bonus;) See the help section on Combat for further details.
Terrain can complicate the movement of units. For instance, moving onto rough terrain such as Mountains can cost land units more than flat terrain like Plains, although sea and air units always expend one movement point to move one tile.
Tiles within range of a city may be worked by that city to produce food, production, and trade points, and the quantity of each produced depends on the terrain. These three products are so important that we specify the output of a tile simply by listing them with slashes in between: for example, "1/2/0" describes a tile that each turn when it is being worked produces one food point, two production points, and no trade points. In addition to the characteristic output of the terrain, some tiles have an additional special resource that boosts one or two of the products. See the Economy section for more information on the use of these products.
The net benefit of a tile for your city depends on your government type as well as city improvements and wonders.
It is possible for your units to change the terrain and hence its effects. see the section on Terrain Alterations for more details.
* You cannot build cities on this terrain.
* Paths cannot be built on this terrain.
* Bases cannot be built on this terrain.
* The coastline of this terrain is unsafe.
* Units on this terrain may impose a zone of control, or be restricted by one.
* Units able to fortify may do so on this terrain.
* No Pollution nor Fallout appear here.
No unit can enter this terrain, nor can any city work its tiles.
* Prevents to build Aqueduct.
* Allows to build Aqueduct, Lake.
* Prevents to build Aqueduct, River.
* You cannot build cities on this terrain.
* Paths cannot be built on this terrain.
* Can be traveled by Missile, Sea, Trireme, Helicopter, and Air units.
* Units on this terrain neither impose zones of control nor are restricted by them.
* No units can fortify on this terrain.
* No Pollution nor Fallout appear here.
Lakes are substantial bodies of fresh water.
* You cannot build cities on this terrain.
* Paths cannot be built on this terrain.
* Can be traveled by Missile, Sea, Trireme, Helicopter, and Air units.
* Units on this terrain neither impose zones of control nor are restricted by them.
* No units can fortify on this terrain.
* Allows cities to build Harbors and coastal wonders.
Shallow oceans are mostly found near coastlines, and are often rich sources of food and other resources.
* You cannot build cities on this terrain.
* Paths cannot be built on this terrain.
* Can be traveled by Missile, Sea, Helicopter, and Air units.
* Units on this terrain neither impose zones of control nor are restricted by them.
* No units can fortify on this terrain.
* Allows cities to build Harbors and coastal wonders.
* No Pollution nor Fallout appear here.
Deep oceans cover much of the world away from coastlines, and only seaworthy units (not including Triremes) can travel on them.
* You cannot build cities on this terrain.
* Can be traveled by Missile, Land, Small Land, Big Land, Merchant, Helicopter, and Air units.
* Units on this terrain may impose a zone of control, or be restricted by one.
* Units able to fortify may do so on this terrain.
* Mine can be upgraded to Oil Well.
Glaciers are found only in the most northerly or southerly reaches of the world. They are very cold, and hence difficult to work with.
* Can be traveled by Missile, Land, Small Land, Big Land, Merchant, Helicopter, and Air units.
* Units on this terrain may impose a zone of control, or be restricted by one.
* Units able to fortify may do so on this terrain.
* Mine can be upgraded to Oil Well.
Deserts are regions of extreme dryness, making agriculture and trade very difficult.
Deserts can be irrigated for a small amount of extra food, but without an oasis or river, bare desert cannot be further improved with farmland.
Rivers bring fertile soil to deserts; on a desert river not already benefiting from an oasis, building irrigation will yield two extra food resources rather than the usual one.
* Can be traveled by Missile, Land, Small Land, Big Land, Merchant, Helicopter, and Air units.
* Units on this terrain may impose a zone of control, or be restricted by one.
* Units able to fortify may do so on this terrain.
Forests are densely wooded, making agriculture somewhat problematic.
* Can be traveled by Missile, Land, Small Land, Big Land, Merchant, Helicopter, and Air units.
* Units on this terrain may impose a zone of control, or be restricted by one.
* Units able to fortify may do so on this terrain.
Grasslands afford exceptional agricultural opportunities.
* Can be traveled by Missile, Land, Small Land, Big Land, Merchant, Helicopter, and Air units.
* Units on this terrain may impose a zone of control, or be restricted by one.
* Units able to fortify may do so on this terrain.
In addition to being amenable to agriculture, Hills are frequently rich in resources.
Cities built in hills are at risk of earthquakes, which can interrupt a city's current project.
* Can be traveled by Missile, Land, Small Land, Merchant, Helicopter, and Air units.
* Units on this terrain may impose a zone of control, or be restricted by one.
* Units able to fortify may do so on this terrain.
Jungles are densely overgrown, making agriculture somewhat problematic. Big Land units may not move into jungle without a road.
* You cannot build cities on this terrain.
* Can be traveled by Missile, Land, Small Land, Merchant, Helicopter, and Air units.
* Units on this terrain may impose a zone of control, or be restricted by one.
* Units able to fortify may do so on this terrain.
Mountains are regions of extreme altitude, making agriculture and trade very difficult.
Land units that move into mountains can see an extra space, but a fast land unit ending its turn in mountains without a road will start its next turn with one fewer movement point. Big Land units may not move into mountains without a road.
* Can be traveled by Missile, Land, Small Land, Big Land, Merchant, Helicopter, and Air units.
* Units on this terrain may impose a zone of control, or be restricted by one.
* Units able to fortify may do so on this terrain.
Plains are very broad, sparse regions, which makes trade slightly inconvenient.
* Can be traveled by Missile, Land, Small Land, Merchant, Helicopter, and Air units.
* Units on this terrain may impose a zone of control, or be restricted by one.
* Units able to fortify may do so on this terrain.
Swamps suffer from an over-abundance of water, making agriculture somewhat problematic. Big Land units may not move in swamps without a road.
* Can be traveled by Missile, Land, Small Land, Big Land, Merchant, Helicopter, and Air units.
* Units on this terrain may impose a zone of control, or be restricted by one.
* Units able to fortify may do so on this terrain.
Tundra are broad, cold regions, fit for some agriculture and little else.